Notes from 3/18/15
Chapter 7
The Central Nervous System
• The brain is a center
for:
• 1. registering
sensations
• 2. correlating with
stored information
• 3. making decisions
• 4. taking action.
2
Landmarks
• Major parts of the brain - cerebrum, cerebellum,
brainstem
3
– brain weighs about 3 pounds, more in anatomy students
Brain
• Longitudinal fissure separates 2 cerebral hemispheres
–
–
–
–
Fissures are deep grooves
sulci the shallow grooves
gyri are the elevated folds
surface layer of gray matter is called the cortex, squash,
noodle
4
Cranial Meninges
• Dura mater -- outermost, tough membrane
– outer periosteal layer against bone
• Arachnoid mater is spider web filamentous layer
• Pia mater is a thin vascular layer adherent to
contours of brain
5
Cranial Meninges
6
Brain Ventricles
Ventricles are Internal chambers within the CNS
7
Cerebrospinal Fluid
• Clear liquid fills ventricles and canals, it flows in
the subarachnoid space
• Functions
– buoyancy -- floats brain so it neutrally buoyant
– protection -- cushions from hitting inside of skull
– chemical stability -- rinses away wastes
8
Flow of Cerebrospinal Fluid
• CSF is formed by
the choroid
plexuses and
• circulates through
the: ventricles,
down central
canal of spinal
cord to
• subarachnoid
space of cord and
brain,
9
• up to be absorbed by
the arachnoid villi of
the dural sinus
Clinical
• If CSF cannot circulate or drain properly a
condition called hydro-cephalus (water on the
brain) develops.
– fluid buildup causes increased
pressure on the brain, either
internally or externally
– Surgically draining the ventricles and diverting the
flow of CSF by an implanted shunt reduces the
pressure
10
Blood-Brain Barrier
• Most materials entering CSF from the blood
cannot leak through the tight junctions
between the surrounding ependymal cells
– permeable to lipid-soluble materials (alcohol, O2,
CO2, nicotine and anesthetics)
• These constitute the Blood-Brain barrier,
which permits certain substances to enter the
fluid but excludes others thereby protecting
the brain and spinal cord from harm
11
The Brain
•
•
•
•
Coordinates body activities
Made up of approximately 100 billion neurons
Uses 20% of bodies oxygen and energy
Divided into three major parts– the Cerebrum
– the Cerebellum
– the Brain Stem (Medulla Oblongata, Pons)
2003-2004
Cerebrum
•
•
•
•
•
Largest part of the brain
Thinking
Memory is stored
Movements are controlled
Impulses from the senses are interpreted.
2003-2004
Gray Matter vs. White Matter
• Gray Matter – Absence of myelin in
masses of neurons accounts for the gray
matter of the brain – Cerebral Cortex
• White Matter - Myelinated neurons gives
neurons a white appearance – inner
layer of cerebrum
Cerebrum specialization
• Regions specialized for different functions
• Lobes
frontal
– frontal
parietal
• speech,
control of emotions
– temporal
• smell, hearing
– occipital
• vision
– parietal
• speech, taste
reading
temporal
2003-2004
occipital